Stress analysis of upsetting with concave curve dies

The stress distributions within the deformation zone in the upsetting of a strain-hardening material by concave curve dies are analyzed in this paper. The geometrical profile of the die surface is constituted by a two-degree polynomial function which has some arbitrary coefficients. The effects of coefficients relating to the geometrical die profile and interface friction on the variations of each stress component are examined. In addition, the forming loads were also calculated for different situations and compared to those obtained by the DEFORM 2D [DEFORM User’s Guide, Scientific Forming Technologies Corporation, Columbus, OH, 1999] finite element package under specific conditions. It is shown that there is a good consistency between theoretical predictions and finite element simulations.